An electronic device containing a polythiophene ##STR00001## wherein R represents a side chain, m represents the number of R substituents; A is a divalent linkage; x, y and z represent, respectively, the number of R.sub.m substituted thienylenes, unsubstituted thienylenes, and divalent linkages A, respectively, in the monomer segment subject to z being 0 or 1, and n represents the number of repeating monomer segments in the polymer or the degree of polymerization.